[PATCH AUTOSEL 6.14 435/642] net/mlx4_core: Avoid impossible mlx4_db_alloc() order value

Sasha Levin
2025-05-05T22:31:26Z

From: Kees Cook <kees@kernel.org>

[ Upstream commit 4a6f18f28627e121bd1f74b5fcc9f945d6dbeb1e ]

GCC can see that the value range for "order" is capped, but this leads
it to consider that it might be negative, leading to a false positive
warning (with GCC 15 with -Warray-bounds -fdiagnostics-details):

../drivers/net/ethernet/mellanox/mlx4/alloc.c:691:47: error: array subscript -1 is below array bounds of 'long unsigned int *[2]' [-Werror=array-bounds=]
691 | i = find_first_bit(pgdir->bits[o], MLX4_DB_PER_PAGE >> o);
| ~~~~~~~~~~~^~~
'mlx4_alloc_db_from_pgdir': events 1-2
691 | i = find_first_bit(pgdir->bits[o], MLX4_DB_PER_PAGE >> o); | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
| | | | | (2) out of array bounds here
| (1) when the condition is evaluated to true In file included from ../drivers/net/ethernet/mellanox/mlx4/mlx4.h:53,
from ../drivers/net/ethernet/mellanox/mlx4/alloc.c:42:
../include/linux/mlx4/device.h:664:33: note: while referencing 'bits'
664 | unsigned long *bits[2];
| ^~~~

Switch the argument to unsigned int, which removes the compiler needing
to consider negative values.

Signed-off-by: Kees Cook <kees@kernel.org>
Link: https://patch.msgid.link/20250210174504.work.075-kees@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/ethernet/mellanox/mlx4/alloc.c | 6 +++---
include/linux/mlx4/device.h | 2 +-
2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/alloc.c b/drivers/net/ethernet/mellanox/mlx4/alloc.c
index b330020dc0d67..f2bded847e61d 100644
--- a/drivers/net/ethernet/mellanox/mlx4/alloc.c
+++ b/drivers/net/ethernet/mellanox/mlx4/alloc.c
@@ -682,9 +682,9 @@ static struct mlx4_db_pgdir *mlx4_alloc_db_pgdir(struct device *dma_device)
}

static int mlx4_alloc_db_from_pgdir(struct mlx4_db_pgdir *pgdir,
- struct mlx4_db *db, int order)
+ struct mlx4_db *db, unsigned int order)
{
- int o;
+ unsigned int o;
int i;

for (o = order; o <= 1; ++o) {
@@ -712,7 +712,7 @@ static int mlx4_alloc_db_from_pgdir(struct mlx4_db_pgdir *pgdir,
return 0;
}

-int mlx4_db_alloc(struct mlx4_dev *dev, struct mlx4_db *db, int order)
+int mlx4_db_alloc(struct mlx4_dev *dev, struct mlx4_db *db, unsigned int order)
{
struct mlx4_priv *priv = mlx4_priv(dev);
struct mlx4_db_pgdir *pgdir;
diff --git a/include/linux/mlx4/device.h b/include/linux/mlx4/device.h
index 27f42f713c891..86f0f2a25a3d6 100644
--- a/include/linux/mlx4/device.h
+++ b/include/linux/mlx4/device.h
@@ -1135,7 +1135,7 @@ int mlx4_write_mtt(struct mlx4_dev *dev, struct mlx4_mtt *mtt,
int mlx4_buf_write_mtt(struct mlx4_dev *dev, struct mlx4_mtt *mtt,
struct mlx4_buf *buf);

-int mlx4_db_alloc(struct mlx4_dev *dev, struct mlx4_db *db, int order);
+int mlx4_db_alloc(struct mlx4_dev *dev, struct mlx4_db *db, unsigned int order);
void mlx4_db_free(struct mlx4_dev *dev, struct mlx4_db *db);

int mlx4_alloc_hwq_res(struct mlx4_dev *dev, struct mlx4_hwq_resources *wqres,
--
2.39.5